Liquid crystal display devices, which have advantages such as non-radiation, light weight, thin thickness and being power-efficient, have been widely used in various electronic products for information, communication and consumption. A liquid crystal display device generally includes a liquid crystal display panel, which includes a pair of substrates disposed opposite to each other and a liquid crystal layer disposed between the pair of substrates. Moreover, in the liquid crystal display panel, thickness of the liquid crystal layer, i.e. a unit thickness, is maintained constant by spacers disposed between the pair of substrates. Typically, spacers in bead shapes diffusedly disposed between the pair of substrates are used. In recent years, however, to improve uniformity of the unit thickness, columnar photosensitive spacers formed and disposed by photo-etching are used between the pair of substrates rather than using the spacers in bead shapes.
FIG. 1 is a plane view of an existing active matrix substrate 110. FIG. 2 is a sectional view of the active matrix substrate 110 and a liquid crystal display panel 100 including the same taken along a line V-V in FIG. 1.
As shown in FIGS. 1 and 2, the liquid crystal display panel 100 includes the active matrix substrate 110, a color filter substrate 120 and a liquid crystal layer 130 between the active matrix substrate 110 and the color filter substrate 120. Photosensitive spacers 123 are provided in the liquid crystal layer 130 to maintain thickness of the liquid crystal display panel 100, and an alignment layer 125 contacting with the liquid crystal layer 130 is disposed on a surface of the color filter substrate 120.
The active matrix substrate 110 includes: a plurality of pixel electrodes 117; a plurality of gate lines 113 extending in parallel to each other along short edges of the respective pixel electrodes 117; a plurality of data lines 115 extending in parallel to each other along long edges of the respective pixel electrodes 117; and a plurality of thin film transistors (TFTs) 105 which are respectively arranged at intersecting portions between the respective gate lines 113 and the respective data lines 115 and respectively connected with the pixel electrodes 117. Moreover, in each pixel regarded as the minimal unit of an image, a TFT 105 is connected with a pixel electrode 117 via a through hole 106 formed at a resin film 101 on the TFT 105. In FIG. 1, the photosensitive spacer 123 is located near an intersecting portion between the gate line 113 and the data line 115, and is formed on the color filter substrate 120 so as to butt against a surface of the active matrix substrate 110 to maintain the unit thickness when a surface of the liquid crystal display panel is pressed.
As mentioned above, in the event that the photosensitive spacers 123 are formed between substrates opposite to each other, problems may be caused in that: an offset may occur when sticking the active matrix substrate 110 and the color filter substrate 120, thus a head portion of the photosensitive spacer 123 on the color filter substrate 120 falls into the interior of the concave through hole 106 formed in the active matrix substrate 110. Therefore, the unit thickness of an area in which the head portion of the photosensitive spacer 123 falls into the interior of the through hole 106 becomes less rather than being maintained constant, so that a stable unit thickness control can hardly be achieved by the photosensitive spacer 123.
In addition, as precision of pixels in the liquid crystal display panel increases, intervals between various data lines 115 become narrower, therefore the photosensitive spacer 123 or the through hole 106 is formed protruding to a light transmission region in a plane view, so as to widen a distance between the through hole 106 and the photosensitive spacer 123 in the plane view. As shown in FIG. 1, the light transmission region here refers to an area, which is not overlapped with the TFT 105, in an area surrounded by a pair of adjacent gate lines 113 and a pair of adjacent data lines 115, and is an area through which light from a backlight source for example may be transmitted so as to be effective for image displaying. When the photosensitive spacer 123 or the through hole 106 protrudes to the light transmission region in the plane view, a portion of the photosensitive spacer 123 or the through hole 106 that protrudes to the light transmission region will eliminate part of the light transmission region, so that the area of an image displaying region is reduced, thus reducing an aperture ratio of the pixel. For example, in the event that the photosensitive spacer 123 is formed protruding to the light transmission region, orientation of the liquid crystal layer near the photosensitive spacer 123 tends to be disordered, so that an area near the photosensitive spacer 123 is obstructed, thus reducing the aperture ratio of the pixel. Moreover, in the event that the through hole 106 is formed protruding to the light transmission region, orientation of the liquid crystal layer near the through hole 106 tends to be disordered, thus reducing the aperture ratio of the pixel due to the same situation mentioned above. Furthermore, light leakage occurs at the area, in which orientation of the liquid crystal layer is disordered, near the photosensitive spacer 123 and the through hole 106, thereby leading to decline of contrast as well. Thus, in the existing liquid crystal display panel, stability of unit thickness control can hardly be maintained through arrangement of the through hole and the photosensitive spacer, and the aperture ratio of a pixel can hardly be maintained.
Further, as precision of pixels in the liquid crystal display panel increases, intervals between various data lines 115 become less, and a non-transmission region between adjacent light transmission regions (i.e. an area covered by a black matrix 121) becomes narrower as well, therefore the photosensitive spacer 123 tends to be deflected to the light transmission region while rubbing-aligning the alignment layer 125, resulting in an increase of area of light leakage in the light transmission region due to the photosensitive spacer 123, and further resulting in a decline of contrast.